[leetcode] Valid Sudoku

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.

The Sudoku board could be partially filled, where empty cells are filled with the character'.'.

A partially filled sudoku which is valid.

Note:
A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.

https://oj.leetcode.com/problems/valid-sudoku/

思路：按照规则，先检查行，然后检查列，然后检查9格。

public class Solution {
	public boolean isValidSudoku(char[][] board) {

		int i;
		for (i = 0; i < 9; i++) {
			if (!isValid(board, i, i + 1, 0, 9))
				return false;
		}

		int j;
		for (j = 0; j < 9; j++) {
			if (!isValid(board, 0, 9, j, j + 1))
				return false;
		}

		for (i = 0; i < 9; i = i + 3)
			for (j = 0; j < 9; j = j + 3) {
				if (!isValid(board, i, i + 3, j, j + 3))
					return false;
			}

		return true;

	}

	private boolean isValid(char[][] board, int iBegin, int iEnd, int jBegin,
			int jEnd) {
		HashSet<Character> set = new HashSet<Character>();
		for (int i = iBegin; i < iEnd; i++)
			for (int j = jBegin; j < jEnd; j++) {
				if (set.contains(board[i][j]))
					return false;
				else if (board[i][j] != '.')
					set.add(board[i][j]);
			}
		return true;

	}

	public static void main(String[] args) {
		char[][] board = { { '5', '3', '.', '.', '7', '.', '.', '.', '.' },
				{ '6', '.', '.', '1', '9', '5', '.', '.', '.' },
				{ '.', '9', '8', '.', '.', '.', '.', '6', '.' },
				{ '8', '.', '.', '.', '6', '.', '.', '.', '3' },
				{ '4', '.', '.', '8', '.', '3', '.', '.', '1' },
				{ '7', '.', '.', '.', '2', '.', '.', '.', '6' },
				{ '.', '6', '.', '.', '.', '.', '2', '8', '.' },
				{ '.', '.', '.', '4', '1', '9', '.', '.', '5' },
				{ '.', '.', '.', '.', '8', '.', '.', '7', '9' } };

		System.out.println(new Solution().isValidSudoku(board));
	}

}